Is it true that you always want what you can’t have? That’s certainly one way to interpret this week’s Field Poll of voter choices in the still-developing race to fill the U.S. Senate seat of the retiring Barbara Boxer.

That poll reflects substantial interest in Condoleezza Rice, the former secretary of state and national security adviser who traded national politics for a comfortable academic perch at Stanford University following George W. Bush’s presidency.

Specifically, the Field Poll found that Rice had the strongest showing, among a list of 18 choices, when likely voters were asked to rate who they would be most inclined to support.

Rice scored 49 percent among those surveyed. Contrast that to the only declared candidate in the race, Attorney General Kamala Harris, who scored 46 percent.

Those numbers are sure to excite Rice’s followers, who see her as an ideal candidate with strong appeal to female and ethnic voters and with deep background in Washington politics and foreign policy. That last point is especially potent in a race for the Senate.

Only trouble is, Rice isn’t running.

She’s made it clear she has no interest in abandoning her professor’s post at Stanford to jump back into the political arena. Virtually every political operative I’ve spoken to doesn’t think that will change. And even if it did, Rice would face tough odds securing a win in Democrat-dominated California in a presidential election year.

That takes us back to Kamala Harris.

The only declared candidate in the Senate race, Harris has been moving to secure key endorsements and to begin the arduous task of raising the millions of dollars it will take to run the campaign. At public events, she’s been ducking questions about her candidacy.

She is the obvious frontrunner at this stage, but the poll indicates voters are keeping a very open mind about who should succeed Sen. Boxer.

Congresswoman Loretta Sanchez of Orange County tallied third in the survey, at 39 percent, followed by California Secretary of State Alex Padilla at 38 percent.

Former Los Angeles Mayor Antonio Villaraigosa, who’s been the object of much speculation, tallied seventh place in the poll with 35 percent support. The question being asked by party insiders is whether Villaraigosa is going to wait much longer to jump into the race.

With the general election 20 months away, the Field Poll in no way is an accurate predictor of the outcome. But it does suggest Boxer’s retirement is opening the door to not just an expensive, but a highly competitive contest in 2016, when presidential politics is sure to boost voter attention and turnout.